Cytotoxic activity of tumor necrosis factor is mediated by early damage of mitochondrial functions. Evidence for the involvement of mitochondrial radical generation
Structural mitochondrial damage accompanies the cytotoxic effects of several drugs including tumor necrosis factor (TNF). Using various inhibitors of mitochondrial electron transport we have investigated the mechanism of TNF-mediated cytotoxicity in L929 and WEHI 164 clone 13 mouse fibrosarcoma cell...
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Veröffentlicht in: | The Journal of biological chemistry 1992-03, Vol.267 (8), p.5317-5323 |
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Zusammenfassung: | Structural mitochondrial damage accompanies the cytotoxic effects of several drugs including tumor necrosis factor (TNF).
Using various inhibitors of mitochondrial electron transport we have investigated the mechanism of TNF-mediated cytotoxicity
in L929 and WEHI 164 clone 13 mouse fibrosarcoma cells. Inhibitors with different sites of action modulated TNF cytotoxicity,
however, with contrasting effects on final cell viability. Inhibition of mitochondrial electron transport at complex III (cytochrome
c reductase) by antimycin A resulted in a marked potentiation of TNF-mediated injury. In contrast, when the electron flow
to ubiquinone was blocked, either at complex I (NADH-ubiquinone oxidoreductase) with amytal or at complex II (succinate-ubiquinone
reductase) with thenoyltrifluoroacetone, cells were markedly protected against TNF cytotoxicity. Neither uncouplers nor inhibitors
of oxidative phosphorylation nor complex IV (cytochrome c oxidase) inhibitors significantly interfered with TNF-mediated effects,
ruling out the involvement of energy-coupled phenomena. In addition, the toxic effects of TNF were counteracted by the addition
of antioxidants and iron chelators. Furthermore, we analyzed the direct effect of TNF on mitochondrial morphology and functions.
Treatment of L929 cells with TNF led to an early degeneration of the mitochondrial ultrastructure without any pronounced damage
of other cellular organelles. Analysis of the mitochondrial electron flow revealed that TNF treatment led to a rapid inhibition
of the mitochondria to oxidize succinate and NADH-linked substrates. The inhibition of electron transport was dose-dependent
and became readily detectable 60 min after the start of TNF treatment, thus preceding the onset of cell death by at least
3-6 h. In contrast, only minor effects were observed on complex IV activity. The different effects observed with the mitochondrial
respiratory chain inhibitors provide suggestive evidence that mitochondrial production of oxygen radicals mainly generated
at the ubisemiquinone site is a causal mechanism of TNF cytotoxicity. This conclusion is further supported by the protective
effect of antioxidants as well as the selective pattern of damage of mitochondrial chain components and characteristic alterations
of the mitochondrial ultrastructure. |
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ISSN: | 0021-9258 1083-351X |
DOI: | 10.1016/s0021-9258(18)42768-8 |